Grinding-mill.



D. COLE.

GRINDING MILL.

APPLICATION FILED NOV. l0, |913- Patented Feb. 22, 1916.

DAVID COLE, F TUCSON, ARIZONA.

GRINDINGr-MILL.

Specification of Letters Patent.

Patented Feb. 22, 1916.

Application led November 10, 1913. Serial No. 800,184.

To all 'whom t may concern:

Be it known that I, DAVID COLE, a citizen of the United States, residing at Tucson, in the county of Pima and State of Arizona, have invented certain new and useful Improvements in Grinding-Mills, of which the following is a specification.

This invention relates to ball or pebble mills of the cylindrical type and particularly to the form of the lining of such mills. In the use of the usual form of cylindrical mill there is a considerable slippage of the charge, detrimental to the results obtained. The purpose of my invention isl to reduce the amount of this slippage and to make use of the slippage that is unavoidable to perform a useful function in causing the larger and heavier particles of the charge to move toward, and accumulate in, the inlet end of the mill where the heavier grinding action takes place, and at the same time to decrease the load in the discharge end of the mill and provide space filled with water, which has a desirable sorting eect upon the material discharged, making it possible to control in suiiicient degree the maximum size of sands to be discharged.

In the drawing I represent my improved lining applied to a simple form of cylindrical mill drum.

Figure 1 is a longitudinal axial section of the drum; and Fig. 2 is a transverse section of the drum looking toward the discharge end.

The supporting and driving mechanism for the mill are not shown and may assume any desired form.

The cylinder or drum is formed with heads 1 and 2, the head 1 having a hollow inlet trunnion 3 and the head 2 a. hollow outlet trunnion 4. These trunnions 3 and 4 are intended to be mounted to turn in the usual bearings (not shown) and thus rotatably support the grinding drum.

heads 1 and 2 are connected by a cylindrical shell 5 having a lining 6, the lining 6 being formed on its inner face with a. preferably continuous spiral corrugation or corrugations 7. The grinding drum thus formed may be rotated on the trunnions 3 and 4 by any familiar driving means, a gear 8 on head l being shown as one example of such means.

The usual grinding elements such as balls,

gravel or the equivalent may be contained in the grinding drum.

' the The Material to be ground, together with an excess of water, is fed in any of the ways familiar to those skilled in this art through hollow inlet trunnion 3, and the water flows out through the hollow outlet trunnion 4,' carrying with it in suspension the finely ground products of the mill. During the grinding action the grinding drum is rotated by power applied through gear 8 in such direction that the corrugations 7 exert on a slipping charge a feeding tendency toward the receiving or inlet end of the drum. The direction of rotation isan essential feature of my invention and may be defined in terms of the spiral pitch of the corrugation or corrugations 7 Where these corrugations have a right hand spiral pitch the drum must be rotated in a right hand or clockwise direction as viewed at the receiving or inlet end by an observer looking toward the discharge end. Where the corrugation or corrugations have a left hand spiral pitch the drum should be rotated in the reverse direction. The efect of this is to maintain the charge at a substantially greater depth at the inlet end and to form a pocket filled with water, deepest at the outlet end, in which ground material is held in suspension while in transit toward the discharge opening. Since the larger particles fall fastest in the water, they come under the influence of the spiral lining and are moved away from the discharge opening until they are ground to sufficient fineness to remain in suspension and be carried by the water past the outlet opening.

The corrugated and spiral form of the lining tends to reduce slippage through the crowding of the charge toward the inlet end of the mill, where the greatest amount of work is to be done, and where the power should be expended. This relieves the discharge end and saves power.

In the drawing I have indicated by the contour lines a-a, b-b, and so on, the form assumed by the charge during the operation of the mill, and from an examination of these and particularly the line f-f at the discharge end it will be observed that the discharge from the mill consists largely of fine particles carried out in suspension in the water. This insures acomparatively even ground product.

While I prefer the use of a continuous spiral corrugation or corrugations it is not essential to my invention that these be continuous, the essential feature being the provision of a spiral conveying means to effect the desired feed toward the head end upon a slipping charge. The spiral corrugations may take slightly different forms from that shown in the drawing and I use the word corrugated in describing the inner surface of my lining to include generally a ribbed or anged surface capable of performing the function specied.

It will be noted that in order to secure the function characteristic of my invention a grinding drum having right hand spiral corrugations must be rotated in a right hand direction (as viewed from the inlet end) and that similarly a drum having left hand spiral corrugations must be rotated in a left hand direction. In certain of the claims I express this relation by the statement that the direction of rotation corresponds to the direction of pitch.

As pointed out, the eHect -of the spiral corrugations is to cause the heavier and larger bodies to move toward the receiving or inlet end of the drum, and the finely ground products to escape at the discharge end, when the drum is rotated in its normal direction of operation. So far as I am aware, no one has heretofore proposed to effect such backward or reverse travel of the larger bodies,-gravel, grinding balls, and the like,-tcward the inlet end of the drum during normal rotation and operation of the mill.

Having thus described my invention, whatnormal grinding direction.

2. In a grindlng mill, the combination .of a substantially cylindrical hollow drum having onits inner face rounded corrugations extending in a reverse or backwardly feeding spiral around said drum in a direction to move the larger bodies of the charge in Contact with said spiral. toward the inlet or receiving end when the drum is rotated in its normal grinding direction, and of a pitch precluding the lifting of material or its carriage over the axis of the drum by said corrugations; hollow inlet and outlet trunnions mounted respectively at opposite ends of said drum, rotatably to support the same; and means for rotating said drum in a direction to effect such movement of the larger boies of the charge toward the receiving en 3. In a grinding mill, the combination of a substantially cylindrical hollow drum adapted to receive material at one end and discharge it, when ground, at the other end; a reversely feeding spiral conveying structure mounted on the inner face of said drum to turn therewith, and adapted to exert a feeding tendency on a charge contained by said drum, through the relative rotationof said drum with respect to said charge; and means for rotating said drum in a direction to cause said conveying structure to urge said charge toward the receiving end of said drum when the drum is turned in its normal grinding direction.

4. In a grinding mill, the combination of a substantially cylindrical imperforate drum adapted to receive material at one end and discharge it, when ground, at the other end; a reversely feeding spiral conveying struc ture mounted on the inner face of said drum to turn therewith, and adapted to urge toward its receiving end a charge within` the drum by reason of the relative rotation of said drum with respect to said charge; and means for rotating said drum in a direction to cause said conveying structure thus to urge said charge toward the receiving end of said drum, the length and diameter of the drum and the pitch of said spiral conveying structure being so proportioned relatively to each other as to produce in the normal op eration of the device, a space adjacent the discharge end containing a relatively small quantity of solid material and a relatively large quantity of water.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

A DAVID COLE.

Witnesses:

LoUIs T. PAYNE, M. J. LANSING. 

